Traditional methods for culturing human embryonic stem cells (hESCs) require the direct use of mouse embryonic fibroblasts (MEFs) as a feeder layer, or feeder-conditioned medium or serum. A medium for a feeder-free culture of hESCs includes an extracellular matrix extracted from a mouse sarcoma and is sold under the trademark Matrigel™ (BD Bioscience, US). Matrigel™ is mostly comprised of laminin and collagen and these compounds in purified form have also been tried in culturing hESCs.
Matrigel™ and the other feeder-free media used currently in cultures suffer from xeno contamination, and in addition are subject to large variability caused by containing growth factors and other undefined molecules.
Mallon B. S. et al. have reviewed the attempts made toward xenofree culture of hESCs in The International Journal of Biochemistry and Cell Biology 38, 1063-1075, 2006. As can be concluded, the culture of hESCs suffers with respect to both technical and clinical potential by the use of cells or extracts originating from animal sources, such as mouse embryonic fibroblasts and an extract from a mouse sarcoma. The current culture methods are also laborious and difficult to scale. Further, it is often hard to maintain the cells in uniform quality and in an undifferentiated form.
One of the biggest problems of the current methods and media for culturing hESCs and embryonic stem cell-like cells, such as iPS cells, arises from the use of animal-derived material in the culture medium.
This problem has now been solved in accordance of the present invention by providing a method for culturing hESCs and/or iPS cells using a medium containing a lectin as a culturing matrix.